As a participating member of the Cooperative Breast Cancer Group under the Clinical Investigations Branch, National Cancer Institute, we are conducting studies with reference to the treatment of advanced breast cancer with various steroid hormones, ablative procedures and other compounds. We plan to continue these studies, as presented in the Group Protocol and its addenda. All investigators agree to follow standardized criteria for acceptance or rejection of patients for study, statistically valid random entry of patients into experimental groups, standardized method and dosage of drug administration, and adequate objective criteria for evaluation of response and review of all cases by qualified extramural investigators. Androgenicity, biologic and other side effects also will be recorded as will subjective response of the patient. Investigations have been carried out with a number of different androgens, estrogens and other steroids. Currently we are adding studies of dose response curves, anti-metabolites, cytotoxic and other chemical agents, ablative procedures (adrenalectomy and hypophysectomy) and the predictive value of urinary steroid excretion levels. Further studies will be carried out aimed at the discovery of new materials and knowledge concerning the effective treatment of breast cancer.